/*    

(d8) THIS PROGRAM REVERSES THE FUNCTION Y EXPRESSED AS


A POWER SERIES IN X.  CALL IT WITH


                      REV(Y,X,N)


WHERE N IS THE TRUNCATION ORDER
*/   


rev(y,x,n):=(y:taylor(y,x,0,n),eq:x = sum(b[i]*y^i,i,1,n),
    sol:solve(makelist(coeff(eq,x,i),i,1,n),makelist(b[i],i,1,n)),y:'y,
    eq:x = sum(b[i]*y^i,i,1,n),eq:ev(eq,sol))$